1. Field of the Invention
The invention relates to heat exchanger devices for cooling fluids used in an engine of a motor vehicle, and more particularly, the invention relates to a heat exchanger package including a coupled radiator and charge air cooler for an engine of a heavy-duty highway truck or bus.
2. Description of Related Art
Heat exchanger packages comprising a radiator and a charge air cooler, also known as an intercooler, have been used for years in over the road highway trucks and buses and other heavy-duty motor vehicles. The radiators provide cooling for the engine coolant, usually a 50—50 solution of water and anti-freeze. The charge air cooler receives compressed, charge or intake air from the turbo- or super-charger and lowers its temperature before it enters the engine intake manifold, thereby making it denser, improving combustion, raising power output and reducing emissions. In order to optimize heat transfer in a given heat exchanger package size, the factors of cooling air flow, heat exchanger core restriction, cooling air flow split and cooling air approach and differential temperature must be balanced.
There is usually limited space availability in the engine compartment for such heat exchanger packages because of sloping hoods covering the engine compartment in the front of trucks, and compact engine compartments in the rear of buses. Both the radiator and the charge air cooler are cooled by the ambient air forced through each by the associated fan and the speed of the vehicle. Because desired cooling capability is continually rising along with the desire for increased engine power and the enactment of new emissions regulations which results in increased heat rejection, enormous demands are placed on the heat exchanger package designer to achieve maximum heat transfer in minimum space.
In one prior art configuration shown in FIG. 1, the charge air cooler (CAC) was arranged in series with and located in front of the engine cooling radiator (RAD) so that it would receive the coolest ambient cooling air. A single suction fan (not shown) usually drew air through the charge air cooler and then through the radiator. The radiator often had to be increased in frontal area as a result of this, because its cooling air was now heated by the charge air cooler.
In order to improve cooling by providing the radiator with lower temperature cooling air, the radiator and charge air cooler were sometimes arranged in parallel, with the charge air cooler located above the radiator or beside the radiator. FIGS. 2 and 3 show prior art radiators and charge air coolers in side-by-side configurations, either vertically (FIG. 1) or horizontally (FIG. 2) aligned, so that the ambient air flows in singularly and parallel through each of the heat exchangers. These designs provide that the face areas of both heat exchangers are exposed to fresh cooling air, rather than only that of the charge air cooler. The radiator can thus be smaller in frontal area, but this design often resulted in a larger overall package frontal area or a limitation on heat transfer surface area. A similar arrangement is shown in U.S. Pat. No. 4,736,727.
Other examples of heat exchanger packages known in the art include the configuration wherein the radiator and charge air cooler are placed behind one another in an overlapping arrangement, as shown in FIGS. 4 and 5. In an effort to optimize heat transfer in a heat exchanger package with minimum frontal area, two completely overlapping charge air coolers have been used, arranged in series with the radiator, and located one in front of the radiator and one behind the radiator, as shown in FIG. 4. In this arrangement, the charge air enters the rear charge air cooler first and then flows through the front charge air cooler. This arrangement allows the first stage of charge air-cooling to be accomplished using warm cooling air exiting the radiator, while the second stage is accomplished with fresh ambient air.
Similar results have been achieved by placing behind the radiator a charge air cooler which has a larger frontal area than the radiator, as in the prior art embodiment shown in FIG. 5. In this configuration, the radiator completely overlaps the charge air cooler, with only a portion of the charge air cooler being non-overlapped. In the overlapping portions, the ambient air flows through the two heat exchangers sequentially in series. This provides some charge air cooling using warm cooling air which has passed through the radiator and some charge air cooling using fresh ambient air in the charge air cooler area not covered by the radiator.
A heat exchanger device used in motor vehicles includes two radiator portions in a vertical, staggered arrangement, as shown in U.S. Pat. No. 5,046,550. However, a partition wall prevents air flowing out of one of the radiator portions from flowing into the other radiator portion. A portion of a condenser for an air conditioning system may be located directly behind the upper radiator to receive air which flows out from that radiator. Another portion of the condenser may be located in front of the lower radiator, with that lower radiator receiving the air exiting the other portion of the condenser. An oil cooler may be placed below the second radiator and ducting prevents air flowing out from the oil cooler from flowing into the lower radiator. Another heat exchanger package is shown in U.S. Patent Application Publication No. US2002/0020365 A1, wherein a radiator and charge air cooler are arranged in a cross packaging where the center portions of each overlap, while the opposite end regions of each extend outward from the center portion without overlap. Other overlapping arrangements are shown in U.S. Pat. No. 6,408,939.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a heat exchanger apparatus which achieves optimized heat transfer using a unique radiator/charge air cooler heat exchanger package arrangement.
It is another object of the present invention to provide a heat exchanger apparatus which provides optimal air flow distributed to specific areas of the radiator/charge air cooler heat exchangers.
It is yet another object of the present invention to provide a method of manufacturing a heat exchanger apparatus which provides various radiator/charge air cooler heat exchanger configurations for optimized cooling.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.